[libvirt] [PATCHv4 06/10] Widening API change - accept empty path for virDomainBlockStats

Michal Privoznik mprivozn at redhat.com
Thu Feb 20 15:26:06 UTC 2014


On 14.02.2014 18:49, Thorsten Behrens wrote:
> And provide domain summary stat in that case, for lxc backend.
> Use case is a container inheriting all devices from the host,
> e.g. when doing application containerization.
> ---
>   src/libvirt.c                |  8 ++++++--
>   tools/virsh-domain-monitor.c | 11 ++++++++---
>   tools/virsh.pod              |  5 +++--
>   3 files changed, 17 insertions(+), 7 deletions(-)

Very wise! We unfortunately can't allow NULL here as it would require 
RPC change (and thus a new API - we have no upstream experience with 
introducing a new version on RPC :))

>
> diff --git a/src/libvirt.c b/src/libvirt.c
> index 666ab1e..b0051bb 100644
> --- a/src/libvirt.c
> +++ b/src/libvirt.c
> @@ -7747,7 +7747,9 @@ error:
>    * an unambiguous source name of the block device (the <source
>    * file='...'/> sub-element, such as "/path/to/image").  Valid names
>    * can be found by calling virDomainGetXMLDesc() and inspecting
> - * elements within //domain/devices/disk.
> + * elements within //domain/devices/disk. Some drivers might also
> + * accept the empty string for the @disk parameter, and then yield
> + * summary stats for the entire domain.
>    *
>    * Domains may have more than one block device.  To get stats for
>    * each you should make multiple calls to this function.
> @@ -7813,7 +7815,9 @@ error:
>    * an unambiguous source name of the block device (the <source
>    * file='...'/> sub-element, such as "/path/to/image").  Valid names
>    * can be found by calling virDomainGetXMLDesc() and inspecting
> - * elements within //domain/devices/disk.
> + * elements within //domain/devices/disk. Some drivers might also
> + * accept the empty string for the @disk parameter, and then yield
> + * summary stats for the entire domain.
>    *
>    * Domains may have more than one block device.  To get stats for
>    * each you should make multiple calls to this function.
> diff --git a/tools/virsh-domain-monitor.c b/tools/virsh-domain-monitor.c
> index de4afbb..105f841 100644
> --- a/tools/virsh-domain-monitor.c
> +++ b/tools/virsh-domain-monitor.c
> @@ -888,7 +888,7 @@ static const vshCmdOptDef opts_domblkstat[] = {
>       },
>       {.name = "device",
>        .type = VSH_OT_DATA,
> -     .flags = VSH_OFLAG_REQ,
> +     .flags = VSH_OFLAG_EMPTY_OK,
>        .help = N_("block device")
>       },
>       {.name = "human",
> @@ -954,8 +954,13 @@ cmdDomblkstat(vshControl *ctl, const vshCmd *cmd)
>       if (!(dom = vshCommandOptDomain(ctl, cmd, &name)))
>           return false;
>
> -    if (vshCommandOptStringReq(ctl, cmd, "device", &device) < 0)
> -        goto cleanup;
> +    /* device argument is optional now. if it's missing, supply empty
> +       string to denote 'all devices'. A NULL device arg would violate
> +       API contract.
> +     */
> +    rc = vshCommandOptStringReq(ctl, cmd, "device", &device); /* and ignore rc */
> +    if (!device)
> +        device = "";

Well, we rather check the return value in a different manner. Although 
this should never return an error.

>
>       rc = virDomainBlockStatsFlags(dom, device, NULL, &nparams, 0);
>
> diff --git a/tools/virsh.pod b/tools/virsh.pod
> index f221475..a13a1c7 100644
> --- a/tools/virsh.pod
> +++ b/tools/virsh.pod
> @@ -623,12 +623,13 @@ If I<--graceful> is specified, don't resort to extreme measures
>   (e.g. SIGKILL) when the guest doesn't stop after a reasonable timeout;
>   return an error instead.
>
> -=item B<domblkstat> I<domain> I<block-device> [I<--human>]
> +=item B<domblkstat> I<domain> [I<block-device>] [I<--human>]
>
>   Get device block stats for a running domain.  A I<block-device> corresponds
>   to a unique target name (<target dev='name'/>) or source file (<source
>   file='name'/>) for one of the disk devices attached to I<domain> (see
> -also B<domblklist> for listing these names).
> +also B<domblklist> for listing these names). On a lxc domain, omitting the
> +I<block-device> yields device block stats summarily for the entire domain.
>
>   Use I<--human> for a more human readable output.
>
>

Michal




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